Former Vice President Al Gore said Monday that the U.S. is “going through a challenging time” under the Trump administration, decrying President Trump’s decision to withdraw from the Paris climate agreement.

“We’ve never had a president who’s deliberately made decisions the effect of which is to tear down America’s standing in the world, starting with his withdrawal from the Paris Agreement,” Gore said Monday on NBC’s “Today Show.” “The climate crisis is by far the most serious challenge we face.”

Trump announced last month that the U.S. would withdraw from the Paris Agreement, an international pact signed by more than 190 countries to commit to fighting climate change by reducing carbon dioxide emissions.

Gore, who has spent much of his time after his 2000 presidential run crusading to fight climate change, met with Trump last year at Trump Tower to discuss climate change.

The meetings had given Gore hope that the president would “come to his senses” about the Paris Agreement.

“But I was wrong,” Gore said. He declined to elaborate on what was discussed in the meeting.

Al Gore speaks during a Q&A following a special screening of “An Inconvenient Sequel: Truth to Power” at Event Cinemas Bondi Junction on July 10, 2017, in Sydney, Australia. (Photo: Brendon Thorne/Getty Images for Paramount Pictures)

“Well, the business community does not believe that at all,” Gore said on CBS’ “Sunday Morning.” “There are now twice as many jobs in the solar industry as in the coal industry.”

In the U.S., the number of solar jobs is growing 17 times faster than the number of jobs in other industries, Gore said, calling the solar industry “one of the brightest spots in our economic revival.”

But the former vice president, who won a Nobel Peace Prize for his climate change work, has faced pushback from some conservatives for his efforts.

“Fox & Friends” criticized Gore for comparing the climate change fight to fights against moral issues such as slavery and apartheid in a July 13 speech at the Ecocity World summit in Australia.

“The climate movement, not least in cities, is right now in the tradition of all the great moral causes that have improved the circumstances of humanity throughout our history,” Gore said in the speech. “The abolition of slavery. Women’s suffrage and women’s rights. The civil rights movement and the anti-apartheid movement in South Africa.”

The longtime climate change battle advocate has taken criticism of his work in stride.

“If everybody’s just completely happy with what you’re doing, you may not be working hard enough to bring about the kind of change that we need,” Gore said on CBS.

He added that he’ll continue to fight climate change, adding, “I could not lay this [fight] down or put it aside even if I wanted to. I don’t want to.”

On NBC, Gore was quick to say that Trump’s decision to leave the Paris Agreement is just one of the ways in which the president has “hurt” America’s “standing in the world,” citing damage to international alliances such as NATO.

“The months ahead will be a test for the American people,” Gore said on NBC.